Infiltration into inclined fibrous sheets

The flow from line and point sources through an inclined fibrous sheet is studied experimentally and theoretically for wicking from a saturated region and flow from a constant-flux source. Wicking from a saturated line generates a wetted region whose length grows diffusively, linearly or tends to a constant, depending on whether the sheet is horizontal or inclined downwards or upwards. A constant-flux line source generates a wetted region which ultimately grows linearly with time, and is characterized by a capillary fringe whose thickness depends on the relative strength of the source, gravitational and capillary forces. Good quantitative agreement is observed between experiments and similarity solutions.Capillary-driven and constant-flux source flows issuing from a point on a horizontal sheet generate a wetted patch whose radius grows diffusively in time. The flow is characterized by the relative strength of the source and spreading induced by the action of capillary forces, gamma. As gamma increases, the fraction of the wetted region which is saturated increases. Wicking from a saturated point corresponds to gamma = gamma(c), and spreads at a slower rate than from a line source. For gamma < gamma(c), the flow is partially saturated everywhere. Good agreement is observed between measured moisture profiles, rates of spreading, and similarity solutions.Numerical solutions are developed for point sources on inclined sheets. The moisture profile is characterized by a steady region circumscribed by a narrow boundary layer across which the moisture content rapidly changes. An approximate analytical solution describes the increase in the size of the wetted region with time and source strength; these conclusions are confirmed by numerical calculations. Experimental measurements of the downslope length are observed to be slightly in excess of theoretical predictions, though the dependence on time, inclination and flow rate obtained theoretically is confirmed. Experimental measurements of cross-slope width are in agreement with numerical results and solutions for short and long times. The affect of a percolation threshold is observed to ultimately arrest cross-slope transport, placing a limitation on the long-time analysis

Friction between a surrogate skin (Lorica Soft) and nonwoven fabrics used in hygiene products

Incontinence pad wearers often suffer from sore skin, and a better understanding of friction between pads and skin is needed to inform the development of less damaging materials. This work investigated friction between a skin surrogate (Lorica Soft) and 13 nonwoven fabrics representing those currently used against the skin in commercial pads. All fabrics were found to behave consistently with Amontons' law: coefficients of friction did not differ systematically when measured under two different loads. Although the 13 fabrics varied considerably in composition and structure, their coefficients of friction (static and dynamic) against Lorica Soft were remarkably similar, especially for the ten fabrics comprising just polypropylene (PP) fibres. The coefficients of friction for one PP fabric never differed by more than 15.7% from those of any other, suggesting that the ranges of fibre decitex (2.0–6.5), fabric area density (13–30 g m−2) and bonding area (11%–25%) they exhibited had only limited impact on their friction properties. It is likely that differences were largely attributable to variability in properties between multiple samples of a given fabric. Of the remaining fabrics, the one comprising polyester fibres had significantly higher coefficients of friction than the highest friction PP fabric (p < 0.005), while the one comprising PP fibres with a polyethylene sheath had significantly lower coefficients of friction than the lowest friction PP fabric (p < 10−8). However, fabrics differed in too many other ways to confidently attribute these differences in friction properties just to the choice of base polymer

Development and psychometric evaluation of ICIQ-PadPROM: A quality of life questionnaire to assess the treatment effect of absorbent continence products

© 2018 Wiley Periodicals, Inc. Aim: To describe the development and evaluation of the ICIQ-PadPROM, the first self-reported quality of life questionnaire to assess the treatment effect of absorbent continence products, a new addition to the set of ICIQ modules providing international standardized assessment of lower pelvic dysfunction. Methods: Developed in four phases, question items semi-structured interviews were conducted with pad using men (n = 19), women (n = 6), with secondary analysis undertaken on transcripts (n = 15 women) from a previous study. Validity of a draft 67 item questionnaire was tested through cognitive debriefing interviews (n = 34) and postal survey (n = 239). Reliability was evaluated by 65 users with a 3 week interval between completions. Expert opinion and factor analysis were used to reduce the final questionnaire to 17 scored and 3 unscored items. Results: The questionnaire comprises four scored domains: Pad design and Physical Effects (seven items), Psychological Effects (four items), Social Effects and Pad Leakage (three items) and Burden of Pad Use (three items), plus three unscored items. Levels of missing data ranged from 0 to 7.6%, with fair-to-moderate agreement. The Cronbach's alpha coefficient for all question items was 0.91 and factor analysis was undertaken to reduce redundancy. Conclusion: Existing incontinence-related outcome tools measure change in symptoms and quality of life impact. The ICIQ PadPROM questionnaire is the first to measure the impact of absorbent continence products on quality of life in the absence of any change in symptoms and will help policy-makers, clinicians, industry, and researchers to evaluate different products designs and materials for different patient populations

A study of friction mechanisms between a surrogate skin (Lorica soft) and nonwoven fabrics.

Hygiene products such as incontinence pads bring nonwoven fabrics into contact with users' skin, which can cause damage in various ways, including the nonwoven abrading the skin by friction. The aim of the work described here was to develop and use methods for understanding the origin of friction between nonwoven fabrics and skin by relating measured normal and friction forces to the nature and area of the contact (fibre footprint) between them. The method development work reported here used a skin surrogate (Lorica Soft) in place of skin for reproducibility. The work was primarily experimental in nature, and involved two separate approaches. In the first, a microscope with a shallow depth of field was used to determine the length of nonwoven fibre in contact with a facing surface as a function of pressure, from which the contact area could be inferred; and, in the second, friction between chosen nonwoven fabrics and Lorica Soft was measured at a variety of anatomically relevant pressures (0.25-32.1kPa) and speeds (0.05-5mms(-1)). Both techniques were extensively validated, and showed reproducibility of about 5% in length and force, respectively. Straightforward inspection of the data for Lorica Soft against the nonwovens showed that Amontons' law (with respect to load) was obeyed to high precision (R(2)>0.999 in all cases), though there was the suggestion of sub-linearity at low loads. More detailed consideration of the friction traces suggested that two different friction mechanisms are important, and comparison with the contact data suggests tentatively that they may correspond to adhesion between two different populations of contacts, one "rough" and one "smooth". This additional insight is a good illustration of how these techniques may prove valuable in studying other, similar interfaces. In particular, they could be used to investigate interfaces between nonwovens and skin, which was the primary motivation for developing them

Quantifying the frictional forces between skin and nonwoven fabrics

When a compliant sheet of material is dragged over a curved surface of a body, the frictional forces generated can be many times greater than they would be for a planar interface. This phenomenon is known to contribute to the abrasion damage to skin often suffered by wearers of incontinence pads and bed/chairbound people susceptible to pressure sores. Experiments that attempt to quantify these forces often use a simple capstan-type equation to obtain a characteristic coefficient of friction. In general, the capstan approach assumes the ratio of applied tensions depends only on the arc of contact and the coefficient of friction, and ignores other geometric and physical considerations; this approach makes it straightforward to obtain explicitly a coefficient of friction from the tensions measured. In this paper, two mathematical models are presented that compute the material displacements and surface forces generated by, firstly, a membrane under tension in moving contact with a rigid obstacle and, secondly, a shell-membrane under tension in contact with a deformable substrate. The results show that, while the use of a capstan equation remains fairly robust in some cases, effects such as the curvature and flaccidness of the underlying body, and the mass density of the fabric can lead to significant variations in stresses generated in the contact region. Thus, the coefficient of friction determined by a capstan model may not be an accurate reflection of the true frictional behavior of the contact region

The Impact of Microclimate on Skin Health With Absorbent Incontinence Product Use An Integrative Review

This integrative review considers the role of skin occlusion and microclimate in incontinence-associated dermatitis (IAD), with a particular focus on disposable, body-worn, absorbent incontinence products. Although the mechanisms are not fully understood, the primary causes of IAD are well-established: occluded skin, in prolonged contact with urine and/or feces and exposed to abrasive forces, is more likely to be affected, and each of these factors can be influenced by wearing absorbent incontinence products. Studies comparing the effect of various absorbent products on skin health have been hindered by the many differences between compared products, making it difficult to clearly attribute any differences in performance to particular materials or design features. Nevertheless, the large and significant differences that have sometimes been found invite further work. Breathable back sheets can significantly reduce the temperature of occluded skin and the humidity of the adjacent air, and several treatments for nonwoven top sheet materials (used next to the skin) have been shown to impart antimicrobial properties in the laboratory, but an impact on IAD incidence or severity has yet to be demonstrated directly. Recent work to introduce sensing technology into absorbent incontinence products to reduce the exposure of skin to urine and feces, by encouraging prompt product changing, seems likely to yield measurable benefits in terms of reducing incidents of IAD as the technology develops. Published work to date suggests that there is considerable potential for products to be engineered to play a significant role in the reduction of IAD among users

A multiscale analysis of frictional interaction between human skin and nonwoven fabrics

Various hygiene products, notably incontinence pads, bring nonwoven “topsheet” fabrics into contact with individuals’ skin. This contact can damage the skin in various ways, including abrading it by friction, a mechanism enhanced by the presence of moisture. In recent years skin-nonwoven friction has been the subject of significant experimental study in the Continence and Skin Technology Group, UCL, in the course of which methods have been developed which can detect differences in friction between a chosen nonwoven and equivalent skin sites on different individuals under fixed conditions. The reasons for these differences are unknown; their elucidation is one focus of this work. The other is to establish the influence of coarse geometry on the dynamics of a tense nonwoven sheet sliding over a substrate and interacting with it by friction. The first part of this work (“microfriction”) is primarily experimental in nature, and involves two separate experiments. The first involves using a microscope with a shallow depth of field to determine the length of nonwoven fibre in contact with a facing surface as a function of pressure; the second consists of measuring friction between chosen nonwovens and a skin surrogate at a variety of pressures and speeds whilst simultaneously observing the behaviour of the interface down a microscope. Both techniques were extensively validated, and the data from the two experiments were then compared. It had originally been intended to conduct the friction experiment on skin (the other experiment does not require it), and though all equipment was developed with this in mind and all relevant permission was sought and obtained, it was not eventually possible. Instead, a skin friction surrogate (Lorica Soft) established in the literature was used. Data from this show that Amontons’ law (with respect to load) is obeyed to high precision (R2 > 0.999 in all cases), though there is the suggestion of sublinearity at low loads. Detailed consideration of the friction traces suggests that two different friction mechanisms are important, and comparison with the contact data suggests tentatively that they may correspond to adhesion between two different populations of contacts, one “rough” and one “smooth”. Further work applying these techniques to skin is necessary. The second aspect of the work is “geometric friction”; that is, the relationship between the geometry of a surface (on the centimetre scale and upwards) and the friction experienced by a compliant sheet (such as nonwoven topsheet) laid over it in tension. A general equation of motion for slippage between sheet and surface has been derived which in principle allows for both objects to deform and interact according to any plausible friction law. This has then been solved in integral form for Amontons’ law and a low density strip exhibiting no Poisson contraction sliding over any surface with zero Gaussian curvature; closed form solutions for the specific cases of a prism and a circular cone have then been derived and compared. Experimental verification has been provided by a colleague, which shows very good agreement between theory and experiment. It has also been shown that, taking a naïve approach, the classic model for a rigid cylinder can be applied even to a quite extreme cone with experimentally negligible error. NB All prior copyrighted material (diagrams in all cases) has been removed from this edition to facilitate electronic distribution. They have been replaced with boxes of the same size, so pagination is identical with the complete version

An investigation of laboratory test methods for predicting the in-use leakage performance of urine-absorbing aids in nursing homes

The absorption before leakage method for measuring the absorption capacity of urine-absorbing aids was investigated. Along with the existing international standard (ISO 11948-1:1996, the Rothwell method), it was run on 12 experimental products whose in-use leakage performance was established by 55 incontinent nursing home residents. Methods were evaluated by considering their simplicity, their repeatability within - and their reproducibility between - six laboratories, and their correlation with in-use product performance. ISO 11948-1:1996 - which measures the absorption capacity of products under simple conditions - showed good repeatability and reproducibility, and reasonable correlation with in-use data. However, it proved blind to the effects of leg cuffs that conferred measurable benefits in real use. It should, therefore, be used with caution. The absorption before leakage method - which measures how much a product will hold before leakage when it is mounted on a manikin and standard aliquots of liquid are applied - is more complex and had poorer repeatability and reproducibility. However, it had stronger correlations with in-use data and successfully detected the benefits of leg cuffs on insert products. It is concluded that it holds potential as a new international standard to replace or complement ISO 11948-1:1996, and the necessary refinement work has been ongoing since the 2007 project described here. Two other laboratory methods were run opportunistically. A rewet method (Spanish national standard UNE 153601-2:2008) - for measuring the escape of fluid from a product under pressure - showed poor repeatability and reproducibility. Finally, an acquisition method was used to measure how quickly products absorbed two successive standard aliquots of liquid. It proved robust, showing good repeatability and reproducibility. Although measurements generally correlated well with in-use leakage performance, a direct causal link is unlikely. Products with high absorption capacity tend also to absorb quickly